1. Field of the Invention
This invention relates to a mechanical pencil in which a lead is automatically fed under a releasing of a slider from a sheet or the like and the slider can be locked at its inner position when the pencil is not used.
2. Description of the Prior Art
In recent years, there has been proposed an automatic mechanical pencil capable of performing a knocking at its rear part having a so-called known one-way chuck type chuck device stored therein in which a lead is held when a writing pressure is applied and a chuck holding action for the lead is released when the lead itself is moved away from the chuck toward a writing extremity end by a resilient force of the slider and a friction applying part inserted into and fitted to the slider under a released writing pressure and then the lead is fed out.
However, any of the prior art pencils has some problems that an inner structure of a lead feeding mechanism or the like is quite complicated, an efficiency of assembling work is also inferior, a large number of component elements are required and a lead is pinched in a lead chuck when used and so a trouble often occurs.
In view of the above-described fact, the present applicant proposed a mechanical pencil in the past by filing Japanese Patent Application No. 62-94905 for a specific structure of the above-mentioned mechanical pencil.
According to this mechanical pencil, the inner structure could be relatively simplified, three types of lead feeding operations (an automatic writing, an extremity end knocking and a rear end knocking) could be carried out, a lock storing of the slider could be performed, a lead was fed out during a lead feeding operation through an extremity knocking action even in case of no projecting of the lead, and in turn, in case that the lead was excessively projected, the lead was not fed out, but only a cushion action was carried out.
Further, in case of a general type of knocking mechanical pencil in which a lead is fed out through knocking action, there was always present a space not covering a lead between a lead chuck for engaging with the lead and feeding-out it and a tip. Due to the presence of this space, it generated problems that a lead was broken or a lead was clogged with broken leads for the sake of no protection of the lead when an external force more than a desired amount was applied to the lead.